Fluid loss additives for cement slurries

ABSTRACT

Methods for cementing in a subterranean zone, which use a cement composition that includes zeolite, cementitious material, proportioned fluid loss control additives and a mixing fluid. Cement compositions containing proportioned fluid loss control additives, and methods of making cement compositions containing proportioned fluid loss control additives.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of prior application Ser. No.10/795,158 filed Mar. 5, 2004, the entire disclosure of which isincorporated herein by reference, which is a continuation-in-part ofprior application Ser. No. 10/738,199 filed Dec. 17, 2003, the entiredisclosure of which is incorporated herein by reference, which is acontinuation-in-part of prior application Ser. No. 10/727,370 filed Dec.4, 2003, the entire disclosure of which is incorporated herein byreference, which is a continuation-in-part of prior application Ser. No.10/686,098 filed Oct. 15, 2003 now U.S. Pat. No. 6,964,302, the entiredisclosure of which is incorporated herein by reference, which is acontinuation-in-part of prior application Ser. No. 10/623,443 filed Jul.18, 2003, the entire disclosure of which is incorporated herein byreference, and which is a continuation-in-part of prior application Ser.No. 10/315,415, filed Dec. 10, 2002 now U.S. Pat. No. 6,989,057, theentire disclosure of which is incorporated herein by reference.

BACKGROUND

The present embodiment relates generally to methods and cementcompositions for cementing in a subterranean zone, and moreparticularly, to cement fluid loss control additives, cementcompositions containing the additives, and methods of using the cementcompositions.

Hydraulic cement compositions are commonly utilized in subterranean wellcompletion and remedial operations. For example, hydraulic cementcompositions are used in primary cementing operations whereby strings ofpipe such as casings and liners are cemented in well bores. Inperforming primary cementing, a hydraulic cement composition is pumpedinto the annular space between the walls of a well bore and the exteriorsurfaces of a pipe string disposed therein. The cement composition ispermitted to set in the annular space, thereby forming an annular sheathof hardened substantially impermeable cement therein, which supports andpositions the pipe string in the well bore and bonds the exteriorsurfaces of the pipe string to the walls of the well bore. Hydrauliccement compositions are also utilized in remedial cementing operationssuch as plugging highly permeable zones or fractures in well bores,plugging cracks or holes in pipe strings, and the like.

Fluid loss control agents are used in cement compositions to reducefluid loss from the cement compositions to the permeable formations orzones into or through which the cement compositions are pumped.

DESCRIPTION

In carrying out certain methods disclosed herein, cementing is performedin a subterranean zone by placing a cement composition comprising amixing fluid, zeolite, cementitious material, and proportioned fluidloss additives (FLAs) as described herein, into the subterranean zoneand allowing the cement composition to set therein.

According to exemplary methods of sealing a wellbore, a cementcomposition is formed by mixing a cement mix, which includes a baseblend and proportioned fluid loss additives (FLAs), with a mixing fluid.The cement composition is placed in the subterranean zone and allowed toset therein. The base blend used in such methods includes zeolite and atleast one cementitious material, and the proportioned FLAs include atleast a first fluid loss additive having a first molecular weight and atleast one second fluid loss additive having a second molecular weightthat is less than the first molecular weight. The first fluid lossadditive will be hereafter referred to as the “high molecular weightFLA” and the second fluid loss additive will be hereafter referred to asthe “low molecular weight FLA”.

According to certain methods disclosed herein, the proportionality ofthe FLAs can be described by a ratio. For example, the proportionalityof the FLAs can be expressed as a ratio of the amounts of each FLA,where each amount is expressed as a weight percent of the total weightof the base blend (% bwob). Thus, in certain examples described herein,the proportionality of the FLAs can be described by a ratio of about15:85, of a high molecular weight FLA to a low molecular weight FLA. Inother examples, the amount of low molecular weight FLAs present in thebase can be increased or decreased, with a complementary increase ordecrease in the amount of high molecular weight FLAs. According to onesuch example, the amount of low molecular weight FLAs in the base blenddecreases to about 0.75% bwob, and the amount of high molecular weightFLAs increases to about 0.25% bwob. In such an example, theproportionality of the FLAs can be described by a ratio of about 25:75of high molecular weight FLAs to low molecular weight FLAs.

In another example, the proportionality of the FLAs can be expressed asa ratio of the amount of high molecular weight FLA(s) to the amount oflow molecular weight FLA(s), irrespective of the amount each typecontributes to the base blend. Thus, in certain examples describedherein, the proportionality of the FLAs can be described as a ratio ofabout 1:5.67, meaning that the amount of low molecular weight FLAspresent in the base blend is about 5.67 times the amount of highmolecular weight FLAs present in the base blend. According to an examplewhere the amount of low molecular weight FLAs present in the base blendhas been decreased, such as to the 0.75% bwob described above, and theamount of high molecular weight FLAs has been increased, such as to0.25% bwob described above, the proportionality of the FLAs can bedescribed by a ratio of about 1:3 of high molecular weight FLAs to lowmolecular weight FLAs.

Yet another way to express the proportionality of the FLAs as a ratio isin terms of their molecular weights. According to certain methods, thehigh molecular weight FLA has a molecular weight in the range of fromabout 800,000 atomic mass units to about 1,200,000 atomic mass units,and the low molecular weight FLA has a molecular weight in the range offrom about 100,000 atomic mass units to about 300,000 atomic mass units.Thus, in certain examples, the proportionality of the FLAs can bedescribed as a ratio of about 12:1, meaning that the molecular weight ofthe high molecular weight FLA would be about 12 times the molecularweight of the low molecular weight FLA. In other examples describedherein, the proportionality is described as a ratio of about 4:1,meaning that the molecular weight of the high molecular weight FLA isabout 4 times the molecular weight of the low molecular weight FLA. Instill other examples, the proportionality of the FLAs can be describedby a ratio of about 2.66:1, meaning that the molecular weight of thehigh molecular weight FLA would be about 2.66 times the molecular weightof the low molecular weight FLA

In carrying out other methods disclosed herein, a cement mix is preparedby forming a base blend comprising zeolite and at least one cementitiousmaterial, and mixing the base blend with proportioned fluid lossadditives as described herein.

Thus, cement compositions and cement mixes as disclosed herein includeproportioned fluid loss additives (FLAs). In certain exemplarycompositions and mixes, the FLAs are non-ionic water based solublepolymers. According to other examples, the FLAs are hydrophobicallymodified non-ionic water based soluble polymers. In certain examplesdescribed herein, the FLAs are unmodified hydroxyethylcelluloses. Instill other examples, the FLAs are hydrophobically modifiedhydroxyethylcelluloses.

Exemplary cement mixes include a base blend and proportioned fluid lossadditives. The base blend includes zeolite and at least one cementitiousmaterial. The proportioned fluid loss additives are as described above,that is, at least one high molecular weight FLA and at least one lowmolecular weight FLA, and where the high molecular weight FLA and thelow molecular weight FLA are present in the base blend in a ratio ofabout 1:5.67. According to certain examples, the high molecular weightFLA comprises a hydroxyethylcellulose having a molecular weight in therange of from about 800,000 atomic mass units to about 1,200,000 atomicmass units, and the low molecular weight FLA comprises ahydroxyethylcellulose having a molecular weight in the range of fromabout 100,000 atomic mass units to about 300,000 atomic mass units.

A variety of cementitious materials can be used in the present methods,mixes and compositions, including but not limited to hydraulic cements.Hydraulic cements set and harden by reaction with water, and aretypically comprised of calcium, aluminum, silicon, oxygen, and/orsulfur. Hydraulic cements include micronized cements, Portland cements,pozzolan cements, gypsum cements, aluminous cements, silica cements, andalkaline cements. According to preferred embodiments, the cementitiousmaterial comprises at least one API Portland cement. As used herein, theterm API Portland cement means any cements of the type defined anddescribed in API Specification 10, 5^(th) Edition, Jul. 1, 1990, of theAmerican Petroleum Institute (the entire disclosure of which is herebyincorporated as if reproduced in its entirety), which includes ClassesA, B, C, G, and H. According to certain embodiments disclosed herein,the cementitious material comprises Class C cement. Those of ordinaryskill in the art will recognize that the preferred amount ofcementitious material is dependent on the type of cementing operation tobe performed.

Zeolites are porous alumino-silicate minerals that may be either anatural or manmade material. Manmade zeolites are based on the same typeof structural cell as natural zeolites and are composed ofaluminosilicate hydrates having the same basic formula as given below.It is understood that as used in this application, the term “zeolite”means and encompasses all natural and manmade forms of zeolites. Allzeolites are composed of a three-dimensional framework of SiO₄ and AlO₄in a tetrahedron, which creates a very high surface area. Cations andwater molecules are entrained into the framework. Thus, all zeolites maybe represented by the crystallographic unit cell formula:M_(a/n)[(AlO₂)_(a)(SiO₂)_(b)]·xH₂Owhere M represents one or more cations such as Na, K, Mg, Ca, Sr, Li orBa for natural zeolites and NH₄, CH₃NH₃, (CH₃)₃NH, (CH₃)₄N, Ga, Ge and Pfor manmade zeolites; n represents the cation valence; the ratio of b:ais in a range of from greater than or equal to 1 to less than or equalto 5; and x represents the moles of water entrained into the zeoliteframework.

Preferred zeolites for use in the cement compositions prepared and usedaccording to the present disclosure include analcime (hydrated sodiumaluminum silicate), bikitaite (lithium aluminum silicate), brewsterite(hydrated strontium barium calcium aluminum silicate), chabazite(hydrated calcium aluminum silicate), clinoptilolitei (hydrated sodiumaluminum silicate), faujasite (hydrated sodium potassium calciummagnesium aluminum silicate), harmotome (hydrated barium aluminumsilicate), heulandite (hydrated sodium calcium aluminum silicate),laumontite (hydrated calcium aluminum silicate), mesolite (hydratedsodium calcium aluminum silicate), natrolite (hydrated sodium aluminumsilicate), paulingite (hydrated potassium sodium calcium barium aluminumsilicate), phillipsite (hydrated potassium sodium calcium aluminumsilicate), scolecite (hydrated calcium aluminum silicate), stellerite(hydrated calcium aluminum silicate), stilbite (hydrated sodium calciumaluminum silicate) and thomsonite (hydrated sodium calcium aluminumsilicate). In exemplary cement compositions prepared and used accordingto the present disclosure, the zeolite is selected from the groupconsisting of analcime, bikitaite, brewsterite, chabazite,clinoptilolite, faujasite, harmotome, heulandite, laumontite, mesolite,natrolite, paulingite, phillipsite, scolecite, stellerite, stilbite, andthomsonite. According to still other exemplary cement compositionsdescribed herein, the zeolite used in the cement compositions comprisesclinoptilolite.

According to still other examples, in addition to proportioned fluidloss additives as described herein, the cement compositions, cementmixes and base blends described herein further comprise additives suchas set retarding agents and set accelerating agents. Suitable setretarding agents include but are not limited to refined lignosulfonates.Suitable set accelerating agents include but are not limited to sodiumsulfate, sodium carbonate, calcium sulfate, calcium carbonate, potassiumsulfate, and potassium carbonate. Still other additives suitable for usein cement compositions comprising proportioned fluid loss additives asdescribed herein include but are not limited to density modifyingmaterials (e.g., silica flour, sodium silicate, microfine sand, ironoxides and manganese oxides), dispersing agents, strength retrogressioncontrol agents and viscosifying agents.

Water in the cement compositions according to the present embodiments ispresent in an amount sufficient to make a slurry of the desired densityfrom the cement mix, and that is pumpable for introduction down hole.The water used to form a slurry can be any type of water, includingfresh water, unsaturated salt solution, including brines and seawater,and saturated salt solution. According to some examples, the water ispresent in the cement composition in an amount of about 22% to about200% by weight of the base blend of a cement mix. According to otherexamples, the water is present in the cement composition in an amount offrom about 40% to about 180% by weight of the base blend of a cementmix. According to still other examples, the water is present in thecement composition in an amount of from about 90% to about 160% byweight of the base blend of a cement mix.

The following examples are illustrative of the methods and compositionsdiscussed above.

EXAMPLE 1

The following describes exemplary cement compositions comprisingproportioned fluid loss control additives as described herein, and theefficacy of such proportioned fluid loss control additives in suchcompositions.

Nine cement compositions (Nos. 1–9) comprising proportioned fluid losscontrol additives were prepared from the ingredients described in Table1A.

TABLE 1A No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 No. 9 BaseBlend Cement 60 60 60 60 60 60 60 60 60 (wt %) Zeolite 40 40 40 40 40 4040 40 40 (wt %) Additive Na₂CO₃ 2.2 0 0 2.2 0 0 2.2 0 0 (% bwob) Na₂SO₄4.4 0 0 4.4 0 0 4.4 0 0 (% bwob) HR-5 0 0 1 0 0 1 0 0 0 (% bwob)Carbitron 20 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 (% bwob) FWCA0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 (% bwob) Mixing Fluid Water94.59 94.59 94.59 126.53 126.53 126.53 150.45 150.45 150.45 (% bwob)D-Air 3000L 0.328 0.328 0.328 0.328 0.328 0.328 0.328 0.328 0.328 (1/sk)Density (kg/m₃) 1500 1500 1500 1400 1400 1400 1350 1350 1350

Cement composition Nos. 1–9 were prepared according to proceduresdescribed in API Specification RP 10B, 22^(nd) edition, 1997, of theAmerican Petroleum Institute, the entire disclosure of which isincorporated herein by reference. Generally, the procedure involvedpreparing a base blend by dry-mixing a cementitious material and zeoliteby hand in a glass jar.

The amount of zeolite and cement comprising the base blend is asdescribed in Table 1A, where “wt %” indicates the weight percentcontributed to the total weight of the base blend. The cementitiousmaterial used in each base blend was Class C. Clinoptilolite, which iscommercially available from C2C Zeolite Corporation of Calgary, Canada,was used as the zeolite in each base blend.

Sodium carbonate and sodium sulfate, in the amounts listed in Table 1A,where “% bwob” indicates a percentage based on the total weight of thebase blend, were dry-mixed into the base blends of those compositionsthat were to undergo fluid loss testing at temperatures equal to or lessthan about 30° C. (i.e., Nos. 1, 4 and 7) to accelerate the set of thecement at such temperatures.

HR-5, which is the tradename for a retarder comprising a refinedlignosulfonate commercially available from Halliburton Energy Services,was dry-mixed into the base blends of cement composition Nos. 3 and 6 inthe amount (% bwob) listed in Table 1A. The retarder served to slow theset time that would otherwise occur at the conditions (density and fluidloss test temperature) of the compositions.

Proportioned fluid loss additives (FLAs) were also dry-mixed into thebase blends used for cement composition Nos. 1–9. In the examplesillustrated in Table 1A, the proportioned fluid loss additives wereCarbitron 20 and FWCA, which were dry-mixed into the base blend in theamounts (% bwob) as listed in Table 1A. Carbitron 20 is an unmodifiednon-hydrophobic hydroxyethylcellulose (HEC) having a molecular weight ofabout 225,000 atomic mass units, (amu), and is commercially availablefrom Dow Chemical. FWCA is an unmodified non-hydrophobichydroxyethylcellulose (HEC) having a molecular weight of about 1,000,000amu, and is commercially available from Halliburton Energy Services.

The respective cement-zeolite base blends, and any acceleratingadditives, retarders, and proportioned fluid loss additives, comprisedcement mixes from which cement composition Nos. 1–9 were formed.

Each cement composition was formed by adding the cement mix to a mixingfluid being maintained in a Waring blender at 4000 RPM. The cement mixwas added to the mixing fluid over a 15 second period. When all of thecement mix was added to the mixing fluid, a cover was placed on theblender and mixing was continued at about 12,000 RPM for about 35seconds. For each cement composition, the mixing fluid included water inthe amounts as indicated in Table 1A. In certain compositions, themixing fluid also included D-Air 3000L as reported in Table 1A. Theamount of water is reported in Table 1A as a % bwob, and the amount ofD-Air 3000L is reported in “1/sk”, which indicates liters of D-Air 3000Lper sack of cement composition. D-Air 3000L is the tradename for adefoaming agent comprising polypropylene glycol, particulate hydrophobicsilica and a liquid diluent, which is commercially available fromHalliburton Energy Services, Duncan, Okla. The cement mix temperatureand mixing fluid temperature were both 24° C. (75° F.).

Cement composition Nos. 1–9 illustrate cement compositions comprisingproportioned fluid loss additives (FLAs). The proportionality of theFLAs can be expressed as a ratio of the amounts of each FLA, where eachamount is expressed as a weight percent of the total weight of the baseblend (% bwob). Thus, in this Example 1, the proportionality of theFLAs, expressed as a ratio of the amounts (% bwob) of each type of FLA,can be described by a ratio of about 15:85, of a high molecular weightFLA to a low molecular weight FLA. In other examples, the amount of lowmolecular weight FLAs present in the base can be increased or decreased,with a complementary increase or decrease in the amount of highmolecular weight FLAs. According to one such example, the amount of lowmolecular weight FLAs in the base blend decreases to about 0.75% bwob,and the amount of high molecular weight FLAs increases to about 0.25%bwob. In such an example, the proportionality of the FLAs can bedescribed by a ratio of about 25:75 of high molecular weight FLAs to lowmolecular weight FLAs.

The proportionality of the FLAs can also be expressed as a ratio of theamount of high molecular weight FLA(s) to the amount of low molecularweight FLA(s), irrespective of the amount each type contributes to thebase blend. Thus, in this Example 1, the proportionality of the FLAs canbe described as a ratio of about 1:5.67, meaning that the amount of lowmolecular weight FLAs present in the base blend is about 5.67 times theamount of high molecular weight FLAs present in the base blend.According to an example where the amount of low molecular weight FLAspresent in the base blend has been decreased, such as to the 0.75% bwobdescribed above, and the amount of high molecular weight FLAs has beenincreased, such as to 0.25% bwob described above, the proportionality ofthe FLAs can be described by a ratio of about 1:3 of high molecularweight FLAs to low molecular weight FLAs.

Yet another way to express the proportionality of the FLAs is in termsof their molecular weights. Thus, in this Example 1, where the highmolecular weight FLA comprises an unmodified non-hydrophobichydroxyethylcellulose (HEC) having a molecular weight of about 1,000,000atomic mass units (amu) and the low molecular weight FLA comprises anunmodified non-hydrophobic HEC having a molecular weight of about225,000 amu, the proportionality of the FLAs can be described as a ratioof about 4:1, meaning that the molecular weight of the high molecularweight FLA(s) present in the base blend is about 4 times the molecularweight of the low molecular weight FLA(s) in the base blend. In otherexamples, the molecular weight of the low molecular weight FLAs can bein the range of from about 100,000 amu to about 300,000 amu, while themolecular weight of the high molecular weight FLA can be in the range orfrom about 800,000 amu to about 1,200,000 amu. Thus, according to anexample where the high molecular weight FLA has a molecular weight ofabout 1,200,000 amu and the low molecular weight FLA about 100,000 amu,the proportionality of the FLAs can be described by a ratio of about12:1, meaning that the molecular weight of the high molecular weight FLAis about 12 times the molecular weight of the low molecular weight FLA.In an example where the high molecular weight FLA has a molecular weightof about 800,000 amu and the low molecular weight FLA has a molecularweight of about 300,000 amu, the proportionality of the FLAs can bedescribed by a ratio of about 2.66:1, meaning that the molecular weightof the high molecular weight is about 2.66 times the molecular weight ofthe low molecular weight FLA.

Referring now to Table 1B, rheological data and fluid loss measurementsof cement composition Nos. 1–9 are reported.

TABLE 1B Rheological Data API Fluid API Fluid Dial Readings (cp) LossTest Loss Temp. 600 300 200 100 60 30 6 3 Temperature (mL/30 No. (° C.)rpm rpm rpm rpm rpm rpm rpm rpm ° C.(° F.) min) 1 30 n/a 196 145 89 6547 34 32 30(86)  84 2 50 245 175 131 84 62 43 21 18 50(122) 76 3 80 9960 39 22 15 10 7 6 80(176) 100 4 30 157 101 75 47 34 25 19 18 30(86) 134 5 50 105 66 48 28 19 12 5 4 50(122) 150 6 80 57 38 23 12 7 5 4 280(176) 176 7 30 108 65 46 26 21 15 10 8 30(86)  227 8 50 57 36 25 15 106 1 0.5 50(122) 243 9 80 54 36 30 25 17 11 8 7 80(176) 364

The rheological data was determined using a Fann Model 35 viscometer.The viscosity was taken as the measurement of the dial reading on theFarm Model 35 at the different rotational speeds as indicated in 600 to3 RPM, and at the temperatures as indicated in Table 1B. There are anumber of theoretical models known to those of ordinary skill in the artthat can be used to convert the values from the dial readings at thedifferent RPM's into viscosity (centipoises). In addition, differentviscometer models use different RPM values, thus, in some instances, ameasurement is not available at a particular RPM value.

The rheological data was determined according to the procedures setforth in Section 12 of the API Specification RP 10B, 22nd Edition, 1997,of the American Petroleum Institute (the entire disclosure of which ishereby incorporated as if reproduced in its entirety). The foregoing APIprocedure was modified in that the initial reading at 300 RPM was takenafter 60 seconds continuous rotation at that speed. Dial readings at200, 100, 60, 30, 6 and 3 were then recorded in descending order at20-second intervals. The final reading at 600 RPM was taken after 60seconds continuous rotation at that speed.

The fluid loss testing was conducted according to procedures set forthin Section 10 of API Recommended Practice 10B, 22^(nd) Edition, 1997, ofthe American Petroleum Institute (the entire disclosure of which ishereby incorporated as if reproduced in its entirety).

The procedures followed were those for testing at temperatures less than1940F, with atmospheric pressure conditioning, and a static fluid losscell. Generally, however, 475 cc of each composition was placed into thecontainer of an atmospheric pressure consistometer commerciallyavailable from Howco. The temperatures of the compositions were adjustedto the test temperatures indicated in Table 1B, (30, 50 and 80° C.). Thetest temperatures were arbitrarily chosen, based on values that areoften encountered as bottom hole circulating temperatures (BHCTs) of avariety of types of wells.

After about 20 minutes, the composition to be tested was stirred, and a5 inch standard fluid loss cell, which was prepared according to theaforemetioned Section 10 of API Recommended Practice 10B, was filled.The test was started within 30 seconds of closing the cell byapplication of nitrogen applied through the top valve. Filtrate wascollected and the volume and time were recorded if blow out occurred inless than 30 minutes or volume recorded at 30 minutes if no blow outoccurred. Thus, to determine the fluid loss data reported in Table 1B,values were calculated as twice the volume of filtrate multiplied by5.477 and divided by the square root of time if blowout occurred, and astwice the volume of filtrate if blowout did not occur within 30 minutes.

The measured fluid loss values (mL of fluid lost/30 min) of cementcomposition Nos. 1–9 illustrate that proportioned fluid loss additivesprovide effective fluid loss control to cement compositions having avariety of densities, and at temperatures at least up to 80° C. (176°F.). In addition, the Theological data of cement composition Nos. 1–9 iswithin acceptable parameters.

Although only a few exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many other modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe following claims.

1. A method of cementing in a subterranean zone comprising: forming a cement composition by mixing a cement mix comprising a base blend and proportioned fluid loss additives with a mixing fluid, which base blend comprises zeolite in an amount of at least 20 weight percent and at least one cementitious material, and which proportioned fluid loss additives comprise at least a first fluid loss additive having a first molecular weight and at least a second fluid loss additive having a second molecular weight, which second molecular weight is less than the first molecular weight, and which first fluid loss additive is present in an amount that is less than the amount of the second fluid loss additive; placing the cement composition into the subterranean zone; and allowing the cement composition to set therein.
 2. The method of claim 1 wherein the zeolite is represented by the formula: M_(a/n)[(AlO₂)_(a)(SiO₂)]·xH₂O where M represents one or more cations selected from the group consisting of Na, K, Mg, Ca, Sr, Li, Ba, NH₄, CH ₃NH₃, (CH₃)₃NH, (CH₃)₄ N, Ga, Ge and P; n represents the cation valence; the ratio of b:a is in a range from greater than or equal to 1 and less than or equal to 5; and x represents the moles of water entrained into the zeolite framework.
 3. The method of claim 1 wherein the zeolite is selected from the group consisting of analcime, bikitaite, brewsterite, chabazite, clinoptilolite, faujasite, harmotome, heulandite, laumontite, mesolite, natrolite, paulingite, phillipsite, scolecite, stellerite, stilbite, and thomsonite.
 4. The method of claim 1 wherein the base blend comprises from about 20 to about 60 weight percent zeolite.
 5. The method of claim 1 wherein the base blend comprises about 40 weight percent zeolite.
 6. The method of claim 1 wherein the first molecular weight is about twelve times as much as the second molecular weight.
 7. The method of claim 1 wherein the first molecular weight is about four times as much as the second molecular weight.
 8. The method of claim 1 wherein the first molecular weight is about 2.66 times as much as the second molecular weight.
 9. The method of claim 1 wherein the first molecular weight is in the range of from about 800,000 atomic mass units to about 1,200,000 atomic mass units, and the second fluid loss additive comprises a hydroxyethylcellulose having a molecular weight in the range of from about 100,000 atomic mass units to about 300,000 atomic mass units.
 10. The method of claim 1 wherein the first molecular weight is about 1,000,000 atomic mass units and the second molecular weight is about 225,000 atomic mass units.
 11. The method of claim 1 wherein the first fluid loss additive is present in the cement mix in an amount of at least about 0.15% by weight of the base blend, and the second fluid loss additive is present in the cement mix in an amount of at least about 0.85% by weight of the base blend.
 12. The method of claim 1 wherein the first fluid loss additive is present in the cement mix in an amount of at least about 0.25% by weight of the base blend, and the second fluid loss additive is present in the cement mix in an amount of at least about 0.75% by weight of the base blend.
 13. The method of claim 1 wherein the first fluid loss and the second fluid loss additive are present in the base blend in a ratio of about 1:3.
 14. The method of claim 1 wherein the proportioned fluid loss additives comprise non-ionic water based soluble polymers.
 15. The method of claim 1 wherein the proportioned fluid loss additives comprise hydrophobically modified non-ionic water based soluble polymers.
 16. The method of claim 1 wherein the proportioned fluid loss additives comprise hydroxyethylcelluloses.
 17. The method of claim 1 wherein the proportioned fluid loss additives comprise hydrophobically modified hydroxyethylcelluloses.
 18. The method of claim 1 wherein the first fluid loss additive comprises a hydroxyethylcellulose having a molecular weight in the range of from about 800,000 atomic mass units to about 1,200,000 atomic mass units, and the second fluid loss additive comprises a hydroxyethylcellulose having a molecular weight in the range of from about 100,000 atomic mass units to about 300,000 atomic mass units.
 19. The method of claim 18 wherein the first molecular weight is about 1,000,000 atomic mass units and the second molecular weight is about 225,000 atomic mass units.
 20. The method of claim 1 wherein the mixing fluid comprises water.
 21. The method of claim 20 wherein the mixing fluid further comprises a defoaming agent.
 22. The method of claim 1 wherein the water is present in a range of about 22% to about 200% by weight of the base blend.
 23. The method of claim 1 wherein the water is present in a range of about 40% to about 180% by weight of the base blend.
 24. The method of claim 1 wherein the water is present in a range of about 90% to about 160% by weight of the base blend.
 25. The method of claim 1 wherein the base blend comprises at least one cementitious material selected from the group consisting of micronized cement, Portland cement, pozzolan cement, gypsum cement, aluminous cement, silica cement, and alkaline cement.
 26. The method of claim 1 wherein the cement composition formed has a density in a range of from about 1350 kg/m³ to about 1500 kg/m³.
 27. The method of claim 1 wherein the cement composition further comprises at least one accelerating additive.
 28. The method of claim 27 wherein the at least one accelerating additive is selected from the group consisting of sodium sulfate, sodium carbonate, calcium sulfate, calcium carbonate, potassium sulfate, and potassium carbonate.
 29. The method of claim 27 wherein the least one accelerating additive is present in an amount of about 0.5% to about 10% by weight of the base blend.
 30. The method of claim 29 wherein the accelerating additive is present in the cement mix in an amount of from about 2% to about 8% by weight of the base blend.
 31. The method of claim 1 wherein the first fluid loss and the second fluid loss additive are present in the base blend in a ratio of about 1:5.67.
 32. A method of cementing in a subterranean zone comprising: placing a cement composition into a subterranean zone; and allowing the cement composition to set therein, wherein the cement composition comprises a base blend, proportioned fluid loss additives, and a mixing fluid, which base blend comprises zeolite in an amount of at least about 20 weight percent, and cementitious material; which proportioned fluid loss additives comprise at least a first fluid loss additive having a first molecular weight and at least a second fluid loss additive having a second molecular weight, which second molecular weight is less than the first molecular weight, and which second fluid loss additive is present in an amount that is at least about three times greater than the amount of the first fluid loss additive.
 33. The method of claim 32 wherein the zeolite is represented by the formula: M_(a/n)[(AlO₂)_(a)(SiO₂)]·xH₂O where M represents one or more cations selected from the group consisting of Na, K, Mg, Ca, Sr, Li, Ba, NH₄, CH₃NH₃, (CH₃)₃NH, (CH₃)₄ N, Ga, Ge and P; n represents the cation valence; the ratio of b:a is in a range from greater than or equal to 1 and less than or equal to 5; and x represents the moles of water entrained into the zeolite framework.
 34. The method of claim 32 wherein the zeolite is selected from the group consisting of analcime, bikitaite, brewsterite, chabazite, clinoptilolite, faujasite, harmotome, heulandite, laumontite, mesolite, natrolite, paulingite, phillipsite, scolecite, stellerite, stilbite, and thomsonite.
 35. The method of claim 32 wherein the first molecular weight is at least about 2.66 times as much as the second molecular weight.
 36. The method of claim 32 wherein the first molecular weight is in the range of from about 800,000 atomic mass units to about 1,200,000 atomic mass units, and the second molecular weight is in the range of from about 100,000 atomic mass units to about 300,000 atomic mass units.
 37. The method of claim 32 wherein the first fluid loss additive is present in an amount of at least about 0.15% by weight of the base blend, and the second fluid loss additive is present in an amount of at least about 0.85% by weight of the base blend.
 38. The method of claim 32 wherein the first fluid loss additive is present in an amount of at least about 0.25% by weight of the base blend, and the second fluid loss additive is present in an amount of at least about 0.75% by weight of the base blend.
 39. The method of claim 32 wherein the proportioned fluid loss additives are selected from the group consisting of non-ionic water based soluble polymers, hydrophobically modified non-ionic water based soluble polymers, hydroxyethylcelluloses and hydrophobically modified hydroxyethylcelluloses.
 40. The method of claim 32 wherein the first fluid loss additive comprises a hydroxyethylcellulose having a molecular weight in the range of from about 800,000 atomic mass units to about 1,200,000 atomic mass units, and the second fluid loss additive comprises a hydroxyethylcellulose having a molecular weight in the range of from about 100,000 atomic mass units to about 300,000 atomic mass units.
 41. The method of claim 32 wherein the mixing fluid comprises water.
 42. The method of claim 41 wherein the mixing fluid further comprises a defoaming agent.
 43. The method of claim 32 wherein the base blend comprises at least one cementitious material selected from the group consisting of micronized cement, Portland cement, pozzolan cement, gypsum cement, aluminous cement, silica cement, and alkaline cement.
 44. The method of claim 32 wherein the cement composition further comprises at least one accelerating additive.
 45. The method of claim 44 wherein the at least one accelerating additive is selected from the group consisting of sodium sulfate, sodium carbonate, calcium sulfate, calcium carbonate, potassium sulfate, and potassium carbonate.
 46. A method of cementing in a subterranean zone comprising: placing a cement composition into a subterranean zone; and allowing the cement composition to set therein, wherein the cement composition comprises a base blend, proportioned fluid loss additives, and a mixing fluid, which base blend comprises zeolite in an amount of at least about 20 weight percent and cementitious material; and which proportioned fluid loss additives comprise at least a first fluid loss additive having a first molecular weight and at least a second fluid loss additive having a second molecular weight, which second molecular weight is less than the first molecular weight, and wherein the second fluid loss additive is present in an amount that is greater than the amount of the first fluid loss additive.
 47. The method of claim 46 wherein the zeolite is represented by the formula: M_(a/n)[(AlO₂)_(a)(SiO₂)_(b)]·xH₂O where M represents one or more cations selected from the group consisting of Na, K, Mg, Ca, Sr, Li, Ba, NH₄, CH₃NH₃, (CH₃)₃NH, (CH₃)4 N, Ga, Ge and P; n represents the cation valence; the ratio of b:a is in a range from greater than or equal to 1 and less than or equal to 5; and x represents the moles of water entrained into the zeolite framework.
 48. The method of claim 46 wherein the zeolite is selected from the group consisting of analcime, bikitaite, brewsterite, chabazite, clinoptilolite, faujasite, harmotome, heulandite, laumontite, mesolite, natrolite, paulingite, phillipsite, scolecite, stellerite, stilbite, and thomsonite.
 49. The method of claim 46 wherein the base blend comprises from about 20 to about 60 weight percent zeolite.
 50. The method of claim 46 wherein the base blend comprises about 40 weight percent zeolite.
 51. The method of claim 46 wherein the first molecular weight is at least about 2.66 times as much as the second molecular weight.
 52. The method of claim 46 wherein the first fluid loss additive is present in an amount of at least about 0.15% by weight of the base blend, and the second fluid loss additive is present in an amount of at least about 0.85% by weight of the base blend.
 53. The method of claim 46 wherein the first fluid loss additive is present in an amount of at least about 0.25% by weight of the base blend, and the second fluid loss additive is present in an amount of at least about 0.75% by weight of the base blend.
 54. The method of claim 46 wherein the first fluid loss additive and the second fluid loss additive are present in the base blend in a ratio of about 1:5.67.
 55. The method of claim 46 wherein the proportioned fluid loss additives comprise non-ionic water based soluble polymers or hydrophobically modified non-ionic water based soluble polymers.
 56. The method of claim 46 wherein the proportioned fluid loss additives comprise hydroxyethylcelluloses or hydrophobically modified hydroxyethylcelluloses.
 57. The method of claim 46 wherein the mixing fluid comprises water.
 58. The method of claim 57 wherein the mixing fluid further comprises a defoaming agent.
 59. The method of claim 46 wherein the base blend comprises at least one cementitious material selected from the group consisting of micronized cement, Portland cement, pozzolan cement, gypsum cement, aluminous cement, silica cement, and alkaline cement.
 60. The method of claim 46 wherein the cement composition further comprises at least one accelerating additive.
 61. The method of claim 60 wherein the at least one accelerating additive is selected from the group consisting of sodium sulfate, sodium carbonate, calcium sulfate, calcium carbonate, potassium sulfate, and potassium carbonate.
 62. The method of claim 60 wherein the accelerating additive is present in an amount of from about 0.5% to about 10% by weight of the base blend. 